The present invention relates generally to a sole structure for a shoe, and more particularly, to an improved sole structure for facilitating a compressive deformation to enhance cushioning properties and for reducing a thrust from the ground.
We proposed a sole structure such as shown in Japanese patent application laying-open publication No. 11-235202 (JP 11-235202). The sole structure is comprised of a plurality of band-shaped wavy corrugated sheets arranged side by side and connections that connect the adjacent wavy corrugated sheets with each other.
Also, Japanese patent application laying-open publication No. 2003-339405 (JP 2003-339405) shows a sole structure composed of an upper plate and a lower plate that are disposed oppositely to each other via a void in the upper and lower direction, and a wavy corrugated plate that is interposed between the upper plate and the lower plate and that has an upwardly convex surface fixedly attached to the upper plate and a downwardly convex surface fixedly attached to the lower plate.
Further, WO 2006/129837 shows a sole structure composed of an upper plate, a wavy corrugated lower plate disposed under the upper plate and having two bulges that form a void with the upper plate, and an elastic block member that couples an upwardly convex portion formed between the two bulges to the upper plate.
In the above-mentioned sole structure shown in JP 11-235202, at the time of a shoe strike onto the ground, each of wavy corrugated portions of the band-shaped wavy corrugated sheets compressively deforms into a more flattened shape and at this time each of the connections is twisted by each of the wavy corrugated portions to function as a torsion bar. As a result, in conjunction with the deformation of each of the wavy corrugated portions of the wavy corrugated sheets, an impact load is absorbed.
However, in this case, since the adjacent band-shaped wavy corrugated sheets are coupled to each other by the connections, the amount of compressive deformation of the wavy corrugated portions of the band-shaped wavy corrugated sheets is restricted.
Also, in the above-mentioned sole structure shown in JP 2003-339405, at the time of a shoe strike onto the ground, each of wavy corrugated portions of the wavy corrugated plate compressively deforms into a more flattened shape and the void between the upper plate and the lower plate thus acts as a cushioning hole to absorb an impact load.
However, in this case, since the upwardly convex surface of the wavy corrugated plate is fixedly attached to the upper plate and the downwardly convex surface of the wavy corrugated plate is fixedly attached to the lower plate and the upwardly and downwardly convex surfaces of the wavy corrugated plate are thus restrained by the upper and lower plates, the amount of compressive deformation of the wavy corrugated portions of the wavy corrugated plate is restricted.
Further, in the above-mentioned sole structure shown in WO 2006/129837, at the time of a shoe strike onto the ground, each of the bulges of the lower plate is compressively deforms into a more flattened shape and the void between the upper and lower plates thus functions as a cushioning hole to absorb an impact load.
In this case, as compared with the sole structures of JP 11-235202 and JP 2003-339405, since the upwardly convex portion between the bulges of the lower plate is connected to the upper plate through the elastic block member a compressive deformation of each of the bulges is relatively facilitated and the cushioning properties are improved.
However, in this case, the lower plate is connected to the upper plate through three connecting portions formed of the elastic block member and front and rear connections. Thereby, a thrust acting from the ground at the time of the shoe strike onto the ground is propagated from the lower plate to the upper plate through these three connecting portions.
On the other hand, there exists a demand in the shoe industry that they want to relieve as much thrust as possible acting from the ground to a shoe wearer's foot at the time of a shoe strike onto the ground.
The present invention is directed to providing a sole structure for a shoe that can facilitate a compressive deformation to improve cushioning properties and that can relieve a thrust from the ground.
Other objects and advantages of the present invention will be obvious and appear hereinafter.